Note 4 - Loans and the Allowance for Loan Losses - Loan Portfolio Allocated by Internal Risk Ratings (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Loans	$ 747,885	$ 619,718
Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Loans	167,770	47,892
Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Loans	74,209	78,785
Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	333,768	316,986
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Loans	27,886	31,181
Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	12,848	14,530
Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Loans	34,894	35,471
Commercial and Residential Portfolio Segments [Member]
Loans	651,375	524,845
Pass [Member] | Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Loans	167,515	47,334
Pass [Member] | Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Loans	73,852	76,620
Pass [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	332,249	309,785
Pass [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Loans	27,808	31,097
Pass [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	12,644	14,253
Pass [Member] | Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Loans	34,378	34,855
Pass [Member] | Commercial and Residential Portfolio Segments [Member]
Loans	648,446	513,944
Special Mention [Member] | Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Loans	252	478
Special Mention [Member] | Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Loans	357	2,165
Special Mention [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	653	4,954
Special Mention [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Loans	0	0
Special Mention [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	0	0
Special Mention [Member] | Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Loans	0	0
Special Mention [Member] | Commercial and Residential Portfolio Segments [Member]
Loans	1,262	7,597
Substandard [Member] | Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Loans	3	80
Substandard [Member] | Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Loans	0	0
Substandard [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	866	2,247
Substandard [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Loans	78	84
Substandard [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	204	277
Substandard [Member] | Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Loans	516	616
Substandard [Member] | Commercial and Residential Portfolio Segments [Member]
Loans	1,667	3,304
Doubtful [Member] | Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Loans	0	0
Doubtful [Member] | Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Loans	0	0
Doubtful [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	0	0
Doubtful [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Loans	0	0
Doubtful [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	0	0
Doubtful [Member] | Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Loans	0	0
Doubtful [Member] | Commercial and Residential Portfolio Segments [Member]
Loans	$ 0	$ 0